Self-heterodyne detection for SNR improvement and distributed phase-shift measurements in BOTDA

In this paper we present a Brillouin optical time domain analysis (BOTDA) sensor that takes advantage of the enhanced characteristics obtained employing self heterodyne optical detection combined with synchronous demodulation. By employing this technique we increase the sensitivity of the sensor and demonstrate experimentally a 12.35 dB enhancement in the SNR compared to conventional direct-detection systems. This detection scheme also enables distributed measurements of the Brillouin phase shift in an optical fiber, which can lead to enhanced BOTDA schemes

Brillouin distributed sensor using RF shaping of pump pulses

We introduce a novel configuration for long-range Brillouin optical time domain analysis (BOTDA) sensors that is based on shaping the pump pulses in the radio frequency instead of the optical domain. This results in a simplified setup that uses just one standard intensity modulator to generate pulses with extremely high extinction ratio (60dB in our experiments). We develop a theoretical model for Brillouin interaction in long distance BOTDA and use simulations to demonstrate that the availability of such pure pulses completely suppresses measurement errors caused by pulse leakage. Finally, experimental results are shown to confirm theoretical predictions. A 25 km fibre is measured with our system and the results compared to those obtained using pump pulses with lower extinction ratios

Archaeological chert artifacts from Atapuerca sites (Burgos, Spain): characterization, causes of decay and selection of compatible consolidating products

Chert tools from Galería and Gran Dolina Caves, located in the Sierra de Atapuerca site complex (Burgos, Spain), were characterized (macro-visual inspection, mineralogical phases, degree of crystallinity, soluble salts, surface morphology and optical surface roughness) and compared to chert samples collected from the surrounding Atapuerca mountain range. The chert tools were studied to determine their causes of decay and for selecting the most compatible conso lidation treatments. It was found that samples solely containing quartz were not significantly altered and required little conservation treatment compared to those that contained quartz and moganite, which were more weathered and powdery, requiring consolidation. The effi cacy of the consolidating products traditionally used by conservators (acrylic resin and ethyl silicate) to preserve these chert remains, together with novel nanoparticle-based products (SiO2 and a mixture of SiO2 and Ca(OH)2 nanoparticles) were assessed in this study. Changes produced by these consolidating products in the physical (surface morphology and cohesion) and aesthetic properties of the chert tools were evaluated using non-destructive techniques (peeling test, spectrophotometry and optical surface roughness), followed by destructive techniques, such as SEM and XRD.This research work was carried out at the Instituto de Geociencias (CSIC-UCM) and was founded by predoctoral fellowship JAE-PreDoc 2010-2014 (CSIC) and the Adaptability and Employment Programme of The European Social Fund (FSE 2007-2013). The characterization analyses and tests were funded by Rafael Fort under Geomaterials Programme (S2009/MAT1629). Research of López-Polín is founded by MINECO-FEDER Project “Comportamiento ecosocial de los homínidos de la Sierra de Atapuerca durante el Cuaternario IV” (CGL2015-65387-C3-1-P); SGR 1040 (AGAUR); 2016PFR-URV-B2-17

Brillouin spectral scanning using the wavelength dependence of the frequency shift

We present a novel Brillouin spectra characterization method based on the Brillouin frequency shift dependence with pump wavelength. It is applied to a Brillouin optical time domain analysis sensor, resulting in a cost effective experimental setup that also avoids pulse leakage distortion in the measured spectra

Technique for embedding fiber optics in metallic structures for Smart material applications

In this paper a technique to embed fiber optic sensors (FOS) to metallic structures is presented and validated opening possibilities to smart metallic structures. The technique is based in widely adopted and low cost TIG welding. A detailed procedure for scaling up is presented in which, Ni and Cu coated fiber optics at first, and Ni coated FBG sensors at last are embedded in Tin coated forged steel ST-52 with Tin alloy wire. Tensile and temperature tests show stable measurements with 1.3pm/µm and 24pm/ºC sensibility in the embedded sensor in a metallic specimen for strain ranges from 0 to 550µm and temperature ranges from 50 to 200ºC.This paper was supported by the project Unidad mixta de investigación NEXT-BEARINGS with reference IN853A 2015/2, funded by the Spanish general government administration and the Xunta de Galicia through GAIN and the Ministry of Industry, Energy and Tourism of Spain. As requested by the sponsors, the logos are depicted in Figure 7. Ander Zornoza would also like to acknowledge the support received from the MEC through the Torres Quevedo grant with reference PTQ-14-06588

Documentación de las intervenciones de conservación restauración del patrimonio arquitectónico: perspectiva histórica, situación actual y tendencias de futuro

La documentación de las intervenciones de conservación-restauración del patrimonio engloba los procesos metodológicos y los registros generados antes, durante y después de las mismas, influyendo en la preservación del patrimonio. El objetivo de esta investigación es analizar el contenido de las recomendaciones y normativas que enmarcan estos procesos, estudiando su evolución hasta la situación actual, tanto en el ámbito internacional como nacional. Para ello se analiza la doctrina internacional, la Ley del Patrimonio Histórico Español, las leyes autonómicas y el anteproyecto de reforma de la LPHE. Los resultados muestran que, en la doctrina internacional, las normativas amplían y complementan las anteriores. En el caso de España, cada comunidad autónoma dispone de leyes territoriales que determinan los procesos de intervención que han de disponer de documentación, aunque con diferencias entre ellas. Finalmente, las actualizaciones normativas recientes presentan la tendencia a incluir la documentación de la conservación-restauración, y a incorporar programas preventivos, como un requerimiento dentro del proyecto de intervención.La participación de J.K está financiada por el Gobierno Vasco a través de ayudas para estudios de doctorado, convocatoria 2019-2020 y posteriores renovaciones

Sensitivity magnification of an interferometric optical fiber sensor with a length-linked virtual reference

Here, it is proposed an alternative to magnify the sensitivity of a single optical fiber interferometric sensor up to two orders of magnitude. The method consists of fabricating the sensing interferometer with a specific length whose spectrum is added to that of a virtual interferometer whose length is linked to the sensing interferometer. In this manner, the spectrum of the sensing and virtual interferometers are made to coincide in a maximum or a minimum. The pattern resulting from said sum has a well-defined envelope that is easy to monitor and correlate with the measurand. Thus, the sensor sensitivity can be magnified as desirable. To demonstrate the method, a microscopic Fabry-Perot interferometer was fabricated and tested as temperature sensor. A temperature sensitivity amplification of 124 times was demonstrated experimentally. The method here proposed may pave the way to practical implementation of the Vernier effect with a single interferometer or resonator.This work was supported in part by the grants PDC2022-133885-100, I + D + i/PID2021-122505OB-C31, TED2021-129959B-C21, funded by MCIN/AEI/10.13039/501100011033, by “ERDF A way of making Europe”, by the “European Union Next Generation EU/PRTR” and by Gobierno Vasco/Eusko Jaurlaritza (IT1452-22); ELKARTEK (KK2021/00082, KK2021/00092, KK2021/108, and KK2022/00080)